I just replaced my rear tire, Michelin CommanderII, for another CommanderII. The edges on both sides of the old one were cupped, but that's probably because I should have replaced it long ago. In fact it was so worn it struggled in corners going from the flat surface up onto to the scalloped edges. It also rode very rough. The new one is,...well,...like a NEW one. Rides better and handles better. But I'm sure that if I run this one way past it's replacement time, the edges on this will will cup too.
I think tire design has a lot to do with it too. In my limited opinion, these newer tires with side slash patterns and no center groove have by design a propensity to cup the longer you let them wear. By contrast I never had any cupping issues with the OEM Dunlop D402, and I ran those way down too.
But I may be wrong.